Effect of Internal Curing as Mitigation to Minimize Alkali-Silica Reaction Damage

Abstract

Internal curing can reduce alkali-silica reaction (ASR) damage in concrete. Alkali reactions with chert in natural sand caused damaging ASR in plain concrete. However, ASR damage was minimal in companion internally cured (IC) concrete in which a portion of the sand was replaced with pre-wetted lightweight aggregate (LWA). IC improved paste quality through a quantitative reduction in paste porosity and unhydrated cement. This was assessed using quantitative paste characterization including image analysis of backscattered electron (BSE) images, quantitative fluorescent intensity assessment, resistivity measurements, and qualitative analyses using SEM-EDS and polarized light microscopy. In concretes with the same water-cement ratio (w/c), IC concrete has denser paste microstructure from increased hydration due to additional water from pre-wetted LWA. Less permeable paste reduced fluid ingress, ASR reaction, and crack propagation. This demonstrates the potential of internal curing as a mitigation tool in reducing damage from ASR when high cement content and potentially reactive aggregates are used.

Grout-concrete interface bond performance: Effect of interface moisture on the tensile bond strength and grout microstructure

“…The area in the large BSE maps corresponding to sand particles in the grout was removed using an image treatment process based on the EDS elemental map of calcium. Specific details of the methodology can be found in Beyene et al [17]. The obtained map of sand particles in the grout was then subtracted from the original large BSE map to obtain the final large paste map, used for the porosity measurements, as illustrated in Figure 3(b).…”

“…The image analysis software ImageJ 1.49v 1 was used for quantification of the porosity in each of the BSE 10-μm wide bands. Specific details of the process to measure porosity are described in Beyene et al [17]. It is important to mention that the pixel size in the images (1 pixel representing 0.2 μm × 0.2 μm) allowed for the quantification of pores ranging from 0.45 μm to 40 μm, herein referred to as capillary pores.…”

Eco-UHPC as Repair Material—Bond Strength, Interfacial Transition Zone and Effects of Formwork Type

“…The obtained images were connected, and the interfacial zone was divided into 10 µm wide sections. The aim was to evaluate variations in the phase composition with increasing distance from the interface [ 48 , 49 ]. Unhydrated cement and porosity were segmented from images based on the greyscale histogram and quantitatively evaluated using the ImageJ software.…”

Cracking, Bond, and Durability Performance of Internally Cured Cementitious Grouts for Prefabricated Bridge Element Connections

“…The quantitative analysis of the distribution of the above-mentioned phases of interest along the interface was performed using ImageJ 1.49j software. Specific details of this quantitative image analysis method are described by the authors elsewhere [35,39]. The lowest detectable pore size (1.3 µm) was dictated by the pixel size at the 1500× magnification which was 0.6 µm by 0.6 µm [40].…”